1. Field of the Invention
This invention relates broadly to intraocular devices and surgery. More particularly, this invention relates to intraocular devices used to protect the corneal endothelium during intraocular surgery.
2. State of the Art
The human eye is generally divided into three chambers, the anterior chamber, the posterior chamber, and larger vitreous space anterior of the retina. The anterior chamber includes a transparent and protective cornea as its front wall and the iris or the colored part of the eye as its posterior division. The iris has a pupil, a physiologically active opening in the center of the iris. The posterior chamber rests immediately behind the iris and the pupil and houses the normally transparent crystalline lens of the eye which transmits and focuses light onto the retina at the posterior aspect of the vitreous chamber. The iris separates the anterior chamber from the posterior chamber, and the pupil in the center of the iris regulates how much of the light passing through the cornea reaches the lens and the retina at the posterior aspect of the vitreous space. A cataract is an opacity of the normally transparent lens which obstructs vision. In order to restore vision, ophthalmic surgery is required to remove the cataract.
During ophthalmic surgery a small incision is made at the surgical limbus where the periphery of the cornea meets the sclera. A viscoelastic fluid is then provided through the incision and into the anterior chamber between the iris and the cornea to maintain proper pressure in the eye and prevent the collapse of the anterior chamber. The pupil is also dilated, either mechanically or pharmacologically. As the physician views the lens through the cornea and dilated pupil, instruments are passed through the incision and operated to break the opacities of the lens into fragments, typically using phacoemulsification. In phacoemulsification, a phaco needle is inserted into the cataractous lens and ultrasonically vibrated to carve away and emulsify the cataract. The emulsion is then aspirated out through an aspiration conduit in the phaco needle, while fluid is simultaneously irrigated into the eye from a fluid tube to maintain proper fluid pressure in the eye in the areas adjacent the lens. The natural lens is then supplanted, or supplemented, with an intraocular lens implanted either anterior or posterior the iris or within a capsular bag of the natural lens. The intraocular lenses described in U.S. Pat. No. 4,077,071 to Freeman, U.S. Pat. No. 4,573,998 to Mazzocco, U.S. Pat. No. 4,769,035 to Kelman, U.S. Pat. No. 5,129,319 to Worst, U.S. Pat. No. 5,258,025 to Federov et al., U.S. Pat. No. 5,433,746 to Namdaran, and U.S. Pat. No. 5,556,400 to Tunis are typical of the types of intraocular lenses used.
Throughout the cataract removal and/or intraocular lens implant procedure, multiple instruments may be manipulated within the anterior chamber at once. The operating physician must take great care to prevent any of the instruments from contacting the fragile underside of the cornea, the endothelium, as any damage to the endothelium is considered non-reversible; the cells of the endothelium are neither repairable nor easily replaced. In addition, great care is taken in trying to prevent fragmented pieces of the hard cataract from scratching the endothelium by quickly removing the cataract from the eye. Furthermore, great care must be taken during insertion of the replacement lens into the eye, as some intraocular replacement lenses can destroy endothelial cells if the replacement lens comes into contact with the cells. However, despite all of the care taken, endothelium damage is not uncommon during cataract surgery, as during phacoemulsification of the cataract, shards of the cataract can break off and hit the endothelium.